1. Field of the Invention
This invention relates to an absorption heat pump and a process for operation of an absorption heat pump.
2. Description of Related Art
In absorption heat pump systems, a solution which contains a refrigerant is heated in a boiling apparatus, for example, by means of a gas burner or oil burner, electrically or also with the aid of additional heat exchangers by means of exhaust heat or solar energy, in order to drive the refrigerant as refrigerant vapor out of the solution. The refrigerant vapor is brought by this process to a high temperature level and high pressure level. The refrigerant vapor is then condensed in a condenser against a heating agent, and thus, supplies heat to the heating agent. The highly cooled and expanded refrigerant is supplied to a vaporizer in which it is vaporized against a medium which supplies ambient energy to the refrigerant and is then supplied to at least one absorber.
The solution which has been depleted of refrigerant from the boiling apparatus is supplied via a heat exchanger to the absorber where the solution which has been depleted of coolant is combined with the refrigerant which has passed through the vaporizer. The resulting solution heat is made available to the expulsion process and the consumer or is channeled only to the consumer. The resulting solution, which is rich in refrigerant from the absorber, is pumped to a high pressure level by means of a solution pump from the low pressure level of the absorber, which corresponds roughly to the vaporization pressure, and is supplied again to the boiling apparatus. Finally, the heating agent which has been heated in the condenser is supplied to a consumer and the heating agent which has been cooled by the consumer is returned to the condenser.
If, in an absorption heat pump system, the heating of the boiling apparatus is turned off, the concentration stratification which prevails in the operation of the absorption heat pump in the boiling apparatus is broken down and brought to the level of the solution which is low in refrigerant. During a transient starting process, first by gradual supply of the rich solution, the concentration stratification which is necessary for steady-state operation in the boiling apparatus can be built up. After the boiling apparatus is turned off, therefore, in the restarting of this system considerable starting time and energy losses must be tolerated.
To overcome these problems, European Patent Application EP-B-0 202 432 and its counterpart U.S. Pat. No. 4,718,243 propose a cycling absorption heat pump system in which the high pressure part and the low pressure part, at standstill, are blocked by solenoid valves in order to minimize the restart losses. The defect in this technology is that, when the burner output is changed, which can be caused for example by temperature fluctuations, heat pump operation is not always ensured.